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Screening Of Lactobacillus Antagonizing Helicobacter Pylori And Preliminary Exploration Of Its Antibacterial Mechanism

Posted on:2021-02-03Degree:MasterType:Thesis
Country:ChinaCandidate:X T QinFull Text:PDF
GTID:2370330602478308Subject:Biological engineering
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The objective of this study was to obtain lactic acid bacteria that can tolerate the gastric environment and can colonize and play a probiotic role in the stomach.Therefore,we evaluate the inhibitory effect of lactic acid bacteria screened from human saliva and feces on Helicobacter pylori in vitro,by analyzing its antibacterial properties and exploring its preliminary mechanism of inhibiting Helicobacter pylori.The main research contents and results were as follows:(1)Screening and identification of lactic acid bacteria against Helicobacter pylori.Eighteen strains of lactic acid bacteria,which have a certain tolerance to acid environment and can produce obvious inhibition zone on CAB medium coated with Helicobacter pylori(ATCC26695),were selected from human intestinal and oral source samples.Subsequently,we numbered the strains according to relevant regulations and save them in the probiotic strains bank of the State Key Laboratory of Food Science and Technology of Nanchang University.(2)The ability of lactic acid bacteria to inhibit Helicobacter pylori were evaluated in vitro.Among these strains,there was no significant difference between the fermentation broth of each isolated lactic acid bacteria and the cell free supernatant(CFS)in againsting Helicobacter pylori.According to the experiment simulating the human gastric environment,12 lactic acid bacteria were screened for resistance to artificial gastric juice at low pH.Combining non-specific adhesion indicators with specific adhesion to GES-1 cells,we finally selected the Lactobacillus salivarius(NCUH062005)as the final tested strain.(3)Preliminary study of substances that inhibit Helicobacter pylori was investigated.First,the supernatant of NCUH062005 was treated in different ways,and the bacteriostatic effect of the supernatant was measured with Helicobacter pylori as indicator bacteria.After that,the thermal stability and broad-spectrum protease sensitivity of non-acid antimicrobial substances in metabolites were analyzed.Results showed that the metabolite of NCUH062005 also contains other unknown substances besides lactic acid,which could inhibit the Helicobacter pylori.These substances are insensitive to catalase,various proteases and heat.We speculated that the possibility that the unknown substances were hydrogen peroxide and macromolecular proteins is excluded.(4)Preliminary exploration of the intervention mechanism of lactic acid bacteria on Helicobacter pylori.NCUH062005 could inhibit the urease activity of Helicobacter pylori was also studied,leading to inhibiting its growth.NCUH062005 can destroy the outer membrane structure of Helicobacter pylori which led to greatly reduce the activity and toxicity of Helicobacter pylori.Three kinds of addition modes(i)adding H.pylori in advance;(ii)after adding Helicobacter pylori;(iii)lactic acid bacteria and Helicobacter pylori added at the same time all could inhibit the adhesion of Helicobacter pylori to GES-1 cells.Among them,the exclusion group pre-added with NCUH062005 had the best effect on reducing Helicobacter pylori adhesion to GES-1 cells,with an inhibition rate of about 50%.NCUH062005 could reduce the amount of pro-inflammatory factor(IL-8)secreted by GES-1 cells stimulated by Helicobacter pylori.
Keywords/Search Tags:Lactic acid bacteria, Helicobacter pylori, Antibacterial substances, Antibacterial mechanism
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